For recordkeeping purposes only, a mariner's official MMC identification number is the individual's social security number. However, a unique serial number, called the mariner reference number, and not the social security number, will appear on the credential.

[USCG-2006-24371, 74 FR 11216, Mar. 16, 2009, as amended by USCG-2004-17914, 78 FR 77888, Dec. 24, 2013]